JP2012134756A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of acquiring signals used for removing optical noises.SOLUTION: In an imaging apparatus, when capturing a still picture, a vertical control circuit 26: collectively exposes a photoelectric conversion part of all the pixels 28 disposed on a pixel part 24; collectively transfers an optical charge accumulated by the photoelectric conversion part, to only a first storage part by driving a first transfer part of all the pixels 28 disposed on the pixel part 24 at the timing of ending the exposure; reads out an electrical charge accumulated on the first storage part as an optical signal via a first amplifier, a first connection part, and a first output signal line; and reads out an electrical charge accumulated on a second storage part as an optical noise signal via a second amplifier, a second connection part, and a second output signal line.

Description

  The present invention relates to an imaging apparatus.

  An imaging device such as a digital camera or a digital video camera is equipped with an imaging device that converts an optical image into an electrical signal. Recently, this imaging device has been changed from a CCD (Charge Coupled Device) to a CMOS (Charge Coupled Device). Complementary Metal Oxide Semiconductor (Complementary Metal Oxide Semiconductor) is shifting its market share.

  A MOS type image pickup device such as a CMOS mounted on the image pickup apparatus sequentially reads out the charges of a large number of pixels arranged in a two-dimensional manner on the image pickup surface. In addition, the exposure end time differs from pixel to pixel (or from line to line), and distortion occurs in the image. Therefore, there is provided a MOS type image pickup device that is configured so that the exposure start time of all the pixels can be made the same and the exposure end time of all the pixels can be made the same (that is, control by a global shutter is possible). Are known. This MOS type image pickup device includes a photoelectric conversion unit such as a photodiode that generates a signal corresponding to an exposure amount, a charge storage unit that temporarily stores signal charges generated in the photoelectric conversion unit, and further includes a charge storage unit. The transistor includes a transistor that functions as a switch when performing transfer or reset.

  As an example of the pixel configuration of such an image sensor, a configuration in which five transistors are provided in one pixel as shown in FIG. 10 is known. FIG. 10 is a circuit diagram showing a circuit configuration of a pixel known conventionally. In the example shown in the figure, the charge storage unit FD is used as an in-pixel memory to enable control by a global shutter. When this image sensor is used in a digital camera, a technique of driving in the following sequence is known to suppress KTC noise (reset noise) (see, for example, Patent Document 1).

(1) The charge storage unit FD is reset by the transistor Mr, and reset data is sequentially read and stored for each line via the amplification transistor Ma and the selection transistor Ms.
(2) The photoelectric conversion units PD of all the pixels are collectively reset by the discharge transistor Mf, and after a predetermined exposure time has elapsed, the pixel data of the photoelectric conversion unit PD is collectively charged via the transfer transistor Mt. Transfer to the storage unit FD.
(3) The pixel data transferred to the charge storage unit FD is sequentially scanned and read for each line via the amplification transistor Ma and the selection transistor Ms, and the reset data stored in (1) is subtracted ( Take the difference).

JP 2005-65184 A

  However, when the imaging device is driven in the sequence as described above, the pixel data of the photoelectric conversion unit PD is transferred to the charge storage unit FD in a lump and then the pixel data transferred to the charge storage unit FD is transferred for each line. External light is incident on the image pickup apparatus even during the period from sequential scanning to readout. When external light is incident on the imaging device, charges may leak from the photoelectric conversion unit PD to the charge storage unit FD. In addition, when external light is incident on the imaging device, charges may be generated by the light directly incident on the charge storage unit FD. Therefore, due to external light incident on the imaging device, charge leakage from the photoelectric conversion unit PD and charges generated by light directly incident on the charge storage unit FD, that is, light noise charges due to external light are accumulated in the charge storage unit FD. Sometimes.

  As a result, there is a problem in that optical noise due to optical noise charges appears in the image captured by the imaging apparatus, and the image quality deteriorates. In particular, when imaging a moving high-brightness subject such as a headlight of a running car, a light noise charge is generated on the moving locus of the high-brightness subject, and the picked-up image also has a high-brightness subject as light noise. The movement trajectory of will be reflected.

  The present invention has been made to solve the above-described problem, and an object thereof is to provide an imaging apparatus capable of acquiring a signal used for removing optical noise.

  The present invention converts incident light into photoelectric charge and stores the photoelectric charge, a first storage part for storing charge, a second storage part for storing charge, and the photoelectric conversion part. A first transfer unit that transfers the photoelectric charge stored in the first storage unit, a second transfer unit that transfers the photoelectric charge stored in the photoelectric conversion unit to the second storage unit, and A first reset unit that resets the charge accumulated in the first accumulation unit; a first amplification unit that amplifies and outputs the charge accumulated in the first accumulation unit; A first connection unit for transmitting the output of the amplifier unit to the first output signal line, a second reset unit for resetting the charge accumulated in the second accumulation unit, and the second accumulation unit A second amplifying unit that amplifies and outputs the charge accumulated in the first output signal, and outputs the second amplifying unit as a second output signal. A plurality of pixels having a second connection section that transmits to the pixel section, and a pixel section in which the pixels are two-dimensionally arranged in a matrix, and when capturing a still image, all the pixels included in the pixel section The photoelectric conversion units of the pixels are collectively exposed, and at the timing of exposure completion, the first transfer units of all the pixels included in the pixel units are driven, and the photoelectric charges accumulated in the photoelectric conversion units are The charge accumulated in the first storage unit is transferred to only one storage unit through the first amplification unit, the first connection unit, and the first output signal line. And reading out the electric charge as the optical signal, and the charge accumulated in the second accumulation unit via the second amplification unit, the second connection unit, and the second output signal line, And a control unit that controls to read out as an optical noise signal. An imaging device for.

  In the imaging apparatus according to the aspect of the invention, the control unit may further drive the first reset unit and the second reset unit before collectively exposing the photoelectric conversion unit, and then the first reset unit. The reset signal of the storage unit and the reset signal of the second storage unit are read out, still image data that is a difference between the optical signal and the reset signal of the first storage unit, the optical noise signal, and the first An image processing unit that generates correction data that is a difference from the reset signal of the second storage unit and generates corrected still image data that is a difference between the still image data and the correction data. Features.

  In the imaging device according to the aspect of the invention, the pixel may belong to any one of a plurality of fields, and the control unit may include the optical signal, the optical noise signal, and the first accumulation unit. And a reset signal for the second accumulation unit is controlled to be read from the first accumulation unit and the second accumulation unit of the pixel belonging to the field for each field. It is characterized by.

  In the imaging device according to the aspect of the invention, the control unit may include the photoelectric conversion unit of the pixel before reading out the reset signal of the first accumulation unit and the reset signal of the second accumulation unit for each field. The photoelectric transfer unit accumulates the photoelectric charge accumulated in the photoelectric conversion unit by driving the first transfer unit or the second transfer unit of the pixel at the exposure end timing. 2 and transferring the charge stored in the first storage unit or the second storage unit as an optical signal for live view display, and for each field, The photoelectric conversion unit of the pixel after reading out the optical noise signal is exposed, and at the timing of completion of exposure, the first transfer unit or the second transfer unit of the pixel is driven to perform the photoelectric conversion. Part The accumulated photocharge is transferred only to the first accumulation unit or the second accumulation unit, and the charge accumulated in the first accumulation unit or the second accumulation unit is used as light for live view display. It is characterized by reading out as a signal.

  According to the present invention, when capturing a still image, the control unit performs batch exposure of the photoelectric conversion units of all the pixels included in the pixel unit, and at the timing of completion of the exposure, The photocharge accumulated in the photoelectric conversion unit by driving one transfer unit is collectively transferred only to the first accumulation unit, and the charge accumulated in the first accumulation unit is transferred to the first amplification unit and the first amplification unit. Read out as an optical signal via the connection portion and the first output signal line, and charges accumulated in the second accumulation portion are converted into the second amplification portion, the second connection portion, and the second connection portion. Is read out as an optical noise signal via the output signal line.

  When external light is incident on the imaging device, light noise charges are accumulated in the first accumulation unit and the second accumulation unit. For this reason, the photocharge and the photonoise charge accumulated by the photoelectric conversion unit are accumulated in the first accumulation unit. Further, only the optical noise charge is accumulated in the second accumulation unit. Therefore, it is possible to acquire a noise component included in the optical signal based on the charge accumulated in the first accumulation unit as an optical noise signal based on the charge accumulated in the second accumulation unit. Therefore, according to the present invention, a signal used for removing optical noise can be acquired.

1 is a block diagram illustrating a configuration of an imaging device according to a first embodiment of the present invention. It is the schematic which showed the structure of the imaging part in the 1st Embodiment of this invention. FIG. 3 is a circuit diagram illustrating a circuit configuration of a pixel according to the first embodiment of the present invention. 3 is a timing chart illustrating operation timings of a global shutter operation of the image sensor according to the first embodiment of the present invention. 3 is a timing chart illustrating operation timings of a global shutter operation of the image sensor according to the first embodiment of the present invention. It is the schematic which showed arrangement | positioning of the combination of the signal wire | line and electric charge storage part in the 1st Embodiment of this invention. 6 is a timing chart illustrating operation timings of a global shutter operation of an image sensor according to a second embodiment of the present invention. In the 2nd Embodiment of this invention, it is the schematic which showed the example of the field at the time of dividing a pixel into two fields. 6 is a timing chart illustrating operation timings of a global shutter operation of an image sensor according to a second embodiment of the present invention. It is the circuit diagram which showed the circuit structure of the pixel known conventionally.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 10 according to the present embodiment. The imaging device 10 can be mounted on an electronic device such as a digital video camera or an endoscope in addition to a digital camera. In the illustrated example, the imaging apparatus 10 includes a lens 1, an imaging unit 2, an image processing unit 3, a display unit 4, a drive control unit 6, a lens control unit 7, a camera control unit 8, and camera operations. Part 9. Although the memory card 5 is also shown in FIG. 1, the memory card 5 is configured to be detachable from the imaging apparatus, and thus may not have a configuration unique to the imaging apparatus 10.

  The lens 1 is a photographic lens for forming an optical image of a subject on an imaging surface of an imaging element (described later) of the imaging unit 2. The imaging unit 2 photoelectrically converts an optical image of a subject formed by the lens 1 into a digital signal and then outputs it as an image signal. The image processing unit 3 performs various digital image processing on the image signal output from the imaging unit 2. The image processing unit 3 includes a first image processing unit 3a that processes an image signal (image data) for recording, and a second image processing unit 3b that processes the image signal for display. The display unit 4 displays an image based on the image signal subjected to image processing for display by the second image processing unit 3b of the image processing unit 3. The display unit 4 can reproduce and display a still image, and can perform live view (LV) display that displays an imaging range in real time.

  The memory card 5 is a recording medium for storing an image signal subjected to image processing for recording by the first image processing unit 3a. The drive control unit 6 controls the operation of the imaging unit 2 based on a command from the camera control unit 8. The lens control unit 7 controls the lens aperture and the focal position based on a command from the camera control unit 8. The camera control unit 8 controls each unit included in the imaging device 10. The camera operation unit 9 is for performing various operation inputs to the imaging device 10. For example, a power switch for turning on and off the imaging device 10, a release button for instructing still image shooting, Examples include a still image shooting mode switch for switching the still image shooting mode between the single shooting mode and the continuous shooting mode.

  Next, the configuration of the imaging unit 2 will be described. FIG. 2 is a schematic diagram illustrating the configuration of the imaging unit 2 in the present embodiment. In the illustrated example, the imaging unit 2 includes an imaging device 21 that is a MOS solid-state imaging device, an AD conversion unit 22, and a noise removal unit 23.

  The image pickup device 21 includes a pixel unit 24 including pixels 28, a column processing circuit 25, a vertical control circuit 26, and a horizontal scanning circuit 27. The control unit according to the claims corresponds to the vertical control circuit 26, for example.

  The image sensor 21 can be performed in a global shutter mode in which the charge accumulation operation of the pixels 28 is controlled collectively for all the pixels. Note that a rolling shutter mode in which the charge accumulation operation of the pixels 28 is controlled for each row may be provided.

  In the pixel portion 24, a plurality of pixels 28 are two-dimensionally arranged in the row direction and the column direction. The vertical control circuit 26 applies a signal for controlling the pixel operation in units of rows to the pixels 28 of the pixel unit 24, and includes a vertical scanning circuit, a reset control unit, and a signal readout control unit. . The pixel signals of the pixels 28 in the row selected and controlled by the vertical control circuit 26 are output to the vertical signal line ReadBus1 or the vertical signal line ReadBus2 (see FIG. 3) provided for each column. The column processing circuit 25 processes the pixel signal output to the vertical signal line ReadBus1 or the vertical signal line ReadBus2 for each column, for example, for noise removal when an amplification operation or a rolling shutter operation of the image sensor is performed. CDS (Correlated Double Sampling) processing is performed. The horizontal scanning circuit 27 outputs the output of the column processing circuit 25 in time series in the order of horizontal arrangement.

  The AD conversion unit 22 converts an analog pixel signal output from the image sensor 21 into a digital pixel signal. Needless to say, when the column processing circuit 25 includes an AD conversion circuit, the AD conversion circuit 22 is unnecessary. The noise removal unit 23 performs noise removal processing on the digital pixel signal output from the AD conversion unit 22 when the image sensor 21 operates with a global shutter.

  Next, the configuration of the pixel 28 will be described. FIG. 3 is a circuit diagram showing a circuit configuration of the pixel 28 in the present embodiment. The photoelectric conversion unit PD generates a photoelectric charge corresponding to the received light. Here, a photodiode is shown as an example of the photoelectric conversion unit PD. The charge transfer units Mtx1 and Mtx2 are configured to transfer the photocharge generated by the photoelectric conversion unit PD to the subsequent charge storage units FD1 and FD2.

  The charge storage units FD1 and FD2 are configured to hold the photocharge generated by the photoelectric conversion unit PD. The amplifying units SF1 and SF2 amplify signals based on the photocharges accumulated in the charge accumulating units FD1 and FD2 and read them out. Here, as an example of the amplifiers SF1 and SF2, a source follower circuit using a MOS transistor including a vertical signal line ReadBus1 or a current source connected to the vertical signal line ReadBus2 is shown. The reset units Mr1 and Mr2 are configured to be able to supply a reference voltage to the charge storage units FD1 and FD2. The selection units Mb1 and Mb2 are configured to select each pixel and to read a signal to the outside for each pixel or each pixel row. The charge discharging unit Mft can discharge the photoelectric conversion unit PD. For example, a MOS transistor can be used as the charge discharging unit Mft. In this case, a semiconductor region having the same polarity as the signal charge constituting a part of the photoelectric conversion unit PD is used as a source, and a semiconductor region (overflow drain region, OFD region) supplied with a power supply voltage is used as a drain. ing.

  As a feature of the present embodiment, the pixel 28 includes one photoelectric conversion unit PD, one charge discharge unit Mft, two charge transfer units Mtx1 and Mtx2, and two charge storage units FD1 and FD2. Two amplification units SF1, SF2, two selection units Mb1, Mb2, and two reset units Mr1, Mr2 are provided. In FIG. 3, a circuit that outputs a signal of the photoelectric conversion unit PD, which includes the charge transfer unit Mt1, the charge storage unit FD1, the reset unit Mr1, the amplification unit SF1, and the selection unit Mb1, is an in-pixel circuit. 281. In addition, a circuit that outputs a signal of the photoelectric conversion unit PD, which includes the charge transfer unit Mt2, the charge storage unit FD2, the reset unit Mr2, the amplification unit SF2, and the selection unit Mb2, is used as an in-pixel circuit 282.

  The first storage unit according to the claims corresponds to, for example, the charge storage unit FD1. A second storage unit according to the claims corresponds to, for example, the charge storage unit FD2. The first transfer unit according to the claims corresponds to, for example, the charge transfer unit Mtx1. The second transfer unit according to the claims corresponds to, for example, the charge transfer unit Mtx2. Moreover, the 1st reset part which concerns on a claim respond | corresponds to reset part Mr1, for example. The second reset unit according to the claims corresponds to, for example, the reset unit Mr2. Moreover, the 1st amplification part which concerns on a claim respond | corresponds to amplification part SF1, for example. Moreover, the 2nd amplification part which concerns on a claim respond | corresponds to amplification part SF2, for example. Moreover, the 1st connection part which concerns on a claim respond | corresponds to selection part Mb1, for example. Moreover, the 2nd connection part which concerns on a claim respond | corresponds to selection part Mb2, for example.

  Next, the operation of the imaging unit 2 will be described. The image pickup device 21 included in the image pickup unit 2 can perform a global shutter operation. Hereinafter, the global shutter operation of the image sensor 21 will be described.

  FIG. 4 illustrates the global shutter operation of the image sensor 21 when the reset signal and the optical signal are sequentially read from the first row of pixels 28 to the nth row of pixels 28 during the reset signal readout period and the optical signal readout period. It is a timing chart which shows operation timing. In the present embodiment, the charge accumulation unit FD1 accumulates the photocharge output from the photoelectric conversion unit PD.

  The horizontal axis of the timing chart shown in the figure indicates time. The vertical direction shows a state in which the pixels 28 arranged in the pixel unit 24 are sequentially selected from the first row to the n-th row (final row), and the signals of the pixels are output. As for the timing of signals applied to the signal line TX1 and the signal line FT, only the timing of signals applied simultaneously to the signal line TX1 and the signal line FT of all the pixels 28 in the pixel unit 24 is shown.

  In the reset signal readout period (timing P1 to timing P2) before performing exposure by the global shutter operation, the horizontal scanning circuit 27 reads out the reset signal of the charge storage portion FD1 under the control of the vertical control circuit 26. In this period, first, the vertical control circuit 26 applies a reset pulse from the signal line RST1 to the transistor Mr1 of each pixel 28 arranged in the first row of the pixel unit 24, thereby accumulating the charge in the first row. The unit FD1 is reset. Furthermore, the vertical control circuit 26 applies a selection pulse from the signal line SEL1 to the selection transistor Mb1 of each pixel 28 in the first row, and causes the charge accumulation unit FD1 to output a reset signal to the vertical signal line ReadBus1. The reset signal is read out and stored in the noise removing unit 23 via the column processing circuit 25, the horizontal scanning circuit 27, and the AD converting unit 22. By performing such an operation from the first row to the n-th row (final row) of the pixel portion 24, the reset signal readout period ends.

  Next, at timing P2, the vertical control circuit 26 simultaneously turns on the charge discharging units Mft of all the pixels 28 via the signal line FT, thereby collectively resetting the photoelectric conversion units PD of all the pixels 28. By simultaneously turning off the charge discharging unit Mft of the pixel 28, exposure (photocharge accumulation) of the photoelectric conversion unit PD is started. At a timing P3 when a predetermined exposure period has elapsed after the start of exposure, the vertical control circuit 26 applies a transfer pulse to the charge transfer units Mtx1 of all the pixels 28 via the signal line TX1 at the same time, during the exposure period. The photocharges stored in the photoelectric conversion unit PD are collectively transferred to the charge storage unit FD1. That is, the exposure of all the pixels 28 is completed at the same time.

  Thereafter, the optical signal readout period (timing P3 to timing P4) is entered, and the vertical control circuit 26 applies a selection pulse from the signal line SEL1 to the selection transistor Mb1 of each pixel 28 in the first row, and thereby the charge accumulation unit FD1. To the vertical signal line ReadBus1, the photocharge accumulated in the charge accumulation unit FD1 is output as an optical signal. This optical signal is read out to the noise removal unit 23 via the column processing circuit 25, the horizontal scanning circuit 27, and the AD conversion unit 22. The noise removing unit 23 performs a differential process between the read optical signal of the charge storage unit FD1 and the reset signal of the charge storage unit FD1 stored in the reset signal readout period, and the optical signal from which noise has been removed is obtained. It is output to the image processing unit 3 as still image data. By performing the above operation on the pixels 28 from the first row to the n-th row (final row) of the pixel unit 24, the optical signal readout period is completed, and a still image during one global shutter operation is obtained. Data is output to the image processing unit 3.

  When acquiring still image data, the photocharges of the photoelectric conversion unit PD are collectively transferred to the charge storage unit FD1, and then the photocharges transferred to the charge storage unit FD1 are sequentially scanned for each line. External light may enter the imaging device 10 until it is read out as an optical signal. Therefore, optical noise charges due to external light may be generated in the charge storage unit FD1. As a result, the photocharge transferred from the photoelectric conversion unit PD and the photonoise charge are stored in the charge storage unit FD1. Therefore, the still image data includes optical noise data due to optical noise charges.

  Therefore, in the present embodiment, a charge storage unit FD2 equivalent to the charge storage unit FD1 is provided, and optical noise data based on the optical noise charge generated in the charge storage unit FD2 is acquired. The acquired optical noise data is referred to as correction data. Since the charge storage unit FD1 and the charge storage unit FD2 are equivalent, the same optical noise charge is generated when the same light is incident. Therefore, the difference data between the still image data based on the signal charge and the light noise charge accumulated by the charge accumulation unit FD1 and the correction data based on the light noise charge accumulated by the charge accumulation unit FD2 is optical noise data. The corrected still image data is obtained by removing.

  The correction data acquisition procedure will be described below. In the present embodiment, when acquiring still image data, correction data, which is data for removing optical noise, is acquired. FIG. 5 shows a case where the reset signal of the charge storage unit FD1, the optical signal stored by the charge storage unit FD1, the reset signal of the charge storage unit FD2, and the optical noise signal stored by the charge storage unit FD2 are read. 6 is a timing chart showing the operation timing of the global shutter operation of the image sensor 21 in FIG. In the present embodiment, the charge accumulation unit FD2 accumulates optical noise charges.

  The horizontal axis of the timing chart shown in the figure indicates time. The vertical direction shows a state in which the pixels 28 arranged in the pixel unit 24 are sequentially selected from the first row to the n-th row (final row), and the signals of the pixels are output. Note that (1) the charge storage unit FD1 indicates the timing of reading a signal stored in the charge storage unit FD1. In addition, (2) the charge storage unit FD2 indicates the timing for reading the charge stored in the charge storage unit FD2. As for the timing of signals applied to the signal line TX1 and the signal line FT, only the timing of signals applied simultaneously to the signal line TX1 and the signal line FT of all the pixels 28 in the pixel unit 24 is shown. Note that the timing for reading the signal accumulated in the charge accumulation unit FD1 is the same as the timing shown in FIG.

  Hereinafter, the correction data acquisition timing will be described. In the present embodiment, correction data is acquired using the in-pixel circuit 282. In the reset signal readout period (timing P1 to timing P2) before exposure by the global shutter operation, the horizontal scanning circuit 27 reads out the reset signal of the charge storage portion FD2 under the control of the vertical control circuit 26. In this period, first, the vertical control circuit 26 applies a reset pulse from the signal line RST2 to the transistor Mr2 of each pixel 28 arranged in the first row of the pixel unit 24, thereby accumulating the charge in the first row. The unit FD2 is reset. Furthermore, the vertical control circuit 26 applies a selection pulse from the signal line SEL2 to the selection transistor Mb2 of each pixel 28 in the first row, and causes the charge accumulation unit FD2 to output a reset signal to the vertical signal line ReadBus2. The reset signal is read out and stored in the noise removing unit 23 via the column processing circuit 25, the horizontal scanning circuit 27, and the AD converting unit 22. By performing such an operation from the first row to the n-th row (final row) of the pixel portion 24, the reset signal readout period ends.

  In the still image exposure period (timing P2 to timing P3), the charge accumulation unit FD2 accumulates optical noise charges that cause optical noise generated inside the charge accumulation unit FD2. Thereafter, in the optical signal readout period (timing P3 to timing P4), the vertical control circuit 26 applies a selection pulse from the signal line SEL2 to the selection transistor Mb2 of each pixel 28 in the first row, and thereby the charge accumulation unit FD2. To output an optical noise signal to the vertical signal line ReadBus2. This optical noise signal is read out to the noise removal unit 23 via the column processing circuit 25, the horizontal scanning circuit 27, and the AD conversion unit 22. The noise removing unit 23 performs a difference process between the read optical noise signal of the charge storage unit FD2 and the reset signal of the charge storage unit FD2 stored in the reset signal readout period, and the optical noise from which the noise has been removed The signal is output to the image processing unit 3 as correction data. By performing the above operation on the pixels 28 from the first row to the n-th row (final row) of the pixel unit 24, the correction data is output to the image processing unit 3 simultaneously with the still image data. .

  By performing the global shutter operation as described above, still image data and correction data are input to the image processing unit 3. The first image processing unit 3a of the image processing unit 3 generates difference data between the input still image data and correction data. Accordingly, the image processing unit 3 can generate corrected still image data from which optical noise has been removed. In addition, the first image processing unit 3 a records the generated corrected still image data on the memory card 5.

  Here, the charges accumulated in the charge accumulation unit FD1 and the charge accumulation unit FD2 will be described in detail. In the imaging signal readout period (timing P3 to timing P4), for example, when there is a moving high-luminance subject, etc., charge leakage from the photoelectric conversion unit PD and light directly incident on the charge accumulation unit FD1 and the charge accumulation unit FD2 Due to the charges generated by the above, photonoise charges are accumulated in the charge accumulation portion FD1 and the charge accumulation portion FD2.

  Since the photocharge accumulated by the photoelectric conversion unit PD is transferred to the charge accumulation unit FD1 at the timing P3 after the still image exposure period ends, the charge accumulated by the charge accumulation unit FD1 is transferred from the photoelectric conversion unit PD. Photo charge and photo noise charge. On the other hand, since no pulse is applied to the signal line TX2 at the timing P3 when the still image exposure period ends, no photocharge is transferred from the photoelectric conversion unit PD to the charge storage unit FD2. Therefore, in the charge storage unit FD2, the photoelectric charge stored by the photoelectric conversion unit PD is not stored, but only the optical noise charge is stored.

  As a result, the corrected still image data from which the optical noise is removed is the difference data between the still image data based on the charges accumulated in the charge accumulation unit FD1 and the correction data based on the charges accumulated in the charge accumulation unit FD2. It becomes.

  In the pixel 28, the arrangement of the combination of the signal line TX1 and the charge storage unit FD1 and the combination of the signal line TX2 and the charge storage unit FD2 are the same in the photoelectric conversion unit PD, for example, as shown in FIG. It is desirable to arrange the sides and the same distance. FIG. 6 is a schematic diagram illustrating an arrangement of a combination of the signal line TX1 and the charge storage unit FD1 and a combination of the signal line TX2 and the charge storage unit FD2 in the present embodiment. In the illustrated example, a combination of the signal line TX1 and the charge storage unit FD1 and a combination of the signal line TX2 and the charge storage unit FD2 are arranged on the right side of the photoelectric conversion unit PD. The distance from the side of the photoelectric conversion unit PD to the combination of the signal line TX1 and the charge storage unit FD1 is the same as the distance from the combination of the signal line TX2 and the charge storage unit FD2. Thereby, the optical noise charges accumulated in the charge accumulation unit FD1 and the charge accumulation unit FD2 become more equal, and a signal that can remove the optical noise more accurately can be acquired.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described. The configuration of the imaging device 10 in the present embodiment is the same as the configuration of the imaging device 10 in the first embodiment. The difference between the present embodiment and the first embodiment is that in this embodiment, the reset charge of the charge storage unit FD1 of the pixel 28, the photocharge stored in the charge storage unit FD1, and the reset charge of the charge storage unit FD2. And reading out the optical noise charge accumulated in the charge accumulation unit FD2 by field readout. The difference between the present embodiment and the first embodiment is that when acquiring still image data and correction data, a live view reset signal and a live view video signal used to display a live view are displayed. Is the point to get.

  Next, the operation of the imaging unit 2 will be described. FIG. 7 is a timing chart showing the timing of the global shutter operation of the image sensor 21 when each signal is read out for each field during the reset signal readout period and the optical signal readout period. The illustrated example shows an example of the operation timing when the pixel 28 is divided into two fields.

  FIG. 8 is a schematic diagram illustrating an example of a field when the pixel 28 is divided into two fields in the present embodiment. In the illustrated example, among the pixels 28 arranged in the pixel unit 24, a pixel group including the pixels 28 in the first row, the third row, the fifth row,. The case where the first pixel (f-A) is used, and the pixel group consisting of the pixels 28 in the second, fourth, sixth,..., (2m) rows is the second field (f-B). (M is an integer of 1 or more).

  Returning to the description of FIG. The example shown in FIG. 7 is different from the example shown in FIG. 4 of the first embodiment, in the reset signal readout period and the optical signal readout period, respectively, in the first field (f-A) and the second field (f -B) shows an example in which a reset signal and an optical signal are read from the pixels 28 included in each field. That is, the order of reading the reset signal and the optical signal from the pixel 28 is different between the example shown in FIG. 4 of the first embodiment and the example shown in FIG. As described above, in the global shutter operation, the order of reading the reset signal and the optical signal from the pixels 28 arranged in the pixel unit 24 does not necessarily need to be read in order from the first row to the last row.

  Next, the operation of the imaging device 10 will be described. FIG. 9 is a timing chart showing the operation timing of the global shutter operation of the image sensor 21 when a live view image (moving image) is acquired during still image shooting in the present embodiment. In the timing chart shown in the drawing, the pixel 28 is divided into two fields of a first field (f-A) and a second field (f-B) as in the example shown in FIG. f-A), the second field (f-B), the reset charge of the charge storage unit FD1 of the pixel 28 included in each field, the photocharge stored in the charge storage unit FD1, and the reset of the charge storage unit FD2. In the example, the charge and the optical noise charge accumulated by the charge accumulation unit FD2 are read. In the present embodiment, as in the first embodiment, the charge storage unit FD1 stores the photocharge output from the photoelectric conversion unit PD, and the charge storage unit FD2 stores the photonoise charge.

  First, when still image shooting is started, in period 1, the imaging apparatus 10 performs rolling in order to acquire a live view reset signal of the charge storage unit FD1 of the pixel 28 included in the first field (f-A). Perform a reset. After the arbitrary period 2 elapses, in the period 3, the imaging device 10 acquires a live view video signal for reading out the photocharge accumulated in the charge accumulation unit FD1 of the pixel 28 included in the first field (f-A). Scan. Thereby, the imaging device 10 can acquire the live view reset signal and the live view video signal of the pixels 28 included in the first field (f-A). The second image processing unit 3b of the image processing unit 3 generates a live view display signal that is a difference signal between the live view video signal and the live view reset signal. Then, the second image processing unit 3b causes the display unit 4 to display a live view image based on the generated live view display signal.

  Thereafter, in period 4, the imaging device 10 performs a rolling scan in order to obtain a reset signal for the charge accumulation unit FD 1 and a reset signal for the charge accumulation unit FD 2 of the pixel 28 included in the first field (f-A). Do. Thereby, the imaging device 10 acquires the reset signal of the charge storage unit FD1 and the reset signal of the charge storage unit FD2 of the pixel 28 included in the first field (f-A). In the period 5 to the period 8, the same processing as that in the period 1 to the period 4 is performed on the pixels 28 included in the second field (f-B). Thereby, in the period 1 to the period 8, two live view display signals, the reset signal of the charge accumulation unit FD1 and the reset signal of the charge accumulation unit FD2 included in all the pixels 28 can be acquired.

  After the period 8 ends, the imaging device 10 applies a pulse to the signal lines FT of all the pixels 28 to reset the photoelectric conversion unit PD. Thereafter, after the period 9 that is the exposure period ends, the imaging device 10 applies a pulse to the signal lines TX1 of all the pixels 28 in a lump to transfer photocharges from the photoelectric conversion unit PD to the charge storage unit FD1. .

  Thereafter, in the period 10, the imaging device 10 performs a rolling scan in order to acquire the optical signal of the charge storage unit FD1 and the optical noise signal of the charge storage unit FD2 of the pixel 28 included in the first field (f-A). I do. Thereby, the imaging device 10 acquires the optical signal of the charge storage unit FD1 and the optical noise signal of the charge storage unit FD2 of the pixel 28 included in the first field (f-A).

  Thereafter, in the period 11, the imaging device 10 performs a rolling reset in order to obtain a live view reset signal of the charge accumulation unit FD <b> 1 of the pixel 28 included in the first field (f−A). After the arbitrary period 12 elapses, in the period 13, the imaging device 10 acquires a live-view video signal for reading out the photocharge accumulated in the charge accumulation unit FD1 of the pixel 28 included in the first field (f-A). Scan. Thereby, the imaging device 10 can acquire the live view reset signal and the live view video signal of the pixels 28 included in the first field (f-A). The second image processing unit 3b of the image processing unit 3 generates a live view display signal that is a difference signal between the live view video signal and the live view reset signal. Then, the second image processing unit 3b causes the display unit 4 to display a live view image based on the generated live view display signal. In the period 14 to the period 17, the same processing as that in the period 10 to the period 13 is performed on the pixels 28 included in the second field (f-B). Thereby, in the period 10 to the period 17, two live view display signals, the optical signal of the charge storage unit FD1 and the optical noise signal of the charge storage unit FD2 included in all the pixels 28 can be acquired.

  In the example shown in FIG. 5, in the reset signal readout period (timing P1 to timing P2) and the optical signal readout period (timing P3 to timing P4) immediately before and immediately after the still image exposure period (timing P2 to timing P3), Since the still image data and the correction data of the pixel 28 are acquired at the same time and the live view reset signal and the live view video signal cannot be acquired, the live view image is not updated. On the other hand, in the example illustrated in FIG. 9, in the period 1 to the period 4, the live view reset signal, the live view video signal, and the static signal are output from the pixels 28 included in the first field (f-A). The image reset signal is acquired. Further, in the period 5 to the period 8 which is a period after the period 1 to the period 4, the live view reset signal, the live view video signal, and the still image are received from the pixel 28 included in the second field (f-B). The image reset signal is acquired. Therefore, when acquiring the reset signal for the still image, the live view reset signal and the live view video signal can be acquired in the period 5 to the period 7 that are closer to the exposure period 9.

  In periods 10 to 13, the live view reset signal, the live view video signal, the still image optical signal, and the optical noise signal are output from the pixels 28 included in the first field (f-A). get. Further, in the period 14 to the period 17 that is a period after the period 10 to the period 13, the live view reset signal, the live view video signal, and the still image from the pixels 28 included in the second field (f-B). An image optical signal and an optical noise signal are acquired. Therefore, when acquiring the still image optical signal and the optical noise signal, the live view reset signal and the live view video signal can be acquired in the period 11 to the period 13 which are closer to the exposure period 9. it can.

  Therefore, at the time of still image shooting, the live view reset signal and the live view video signal can be acquired a plurality of times, and the live view reset signal and the live view video signal can be obtained even in a period closer to the exposure period. Since it can be acquired a plurality of times, the period during which the live view image is not updated (blackout period) can be shortened.

  Also in the present embodiment, as in the first embodiment, optical noise correction data for correcting optical noise can be obtained,

  In the present embodiment, the field reading example divided into the first field (f-A) and the second field (f-B) has been described. However, the present invention is not limited to this. The field reading may be performed by dividing. In the present embodiment, the live view reset signal and the live view video signal are acquired from the pixels 28 included in the first field (f-A). However, the present invention is not limited to this, and the second field (f-B). The live view reset signal and the live view video signal may be acquired from the pixels 28 included in the. Even when the live view reset signal and the live view video signal are acquired from the pixels 28 included in the second field (f-B), the period during which the live view image is not updated during still image shooting can be shortened.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Lens, 2 ... Imaging part, 3 ... Image processing part, 3a ... 1st image processing part, 3b ... 2nd image processing part, 4 ... Display part, 5. ..Memory card, 6 ... drive control unit, 7 ... lens control unit, 8 ... camera control unit, 9 ... camera operation unit, 10 ... imaging device, 21 ... imaging device 22 ... AD converter, 23 ... noise remover, 24 ... pixel unit, 25 ... column processing circuit, 26 ... vertical control circuit, 27 ... horizontal scanning circuit, 28. ..Pixels, 281, 282 ... In-pixel circuits

Claims (4)

A photoelectric conversion unit that converts incident light into photoelectric charge and accumulates the photoelectric charge; and
A first accumulation unit for accumulating charges;
A second accumulation unit for accumulating electric charges;
A first transfer unit that transfers the photoelectric charge stored in the photoelectric conversion unit to the first storage unit;
A second transfer unit that transfers the photoelectric charge stored in the photoelectric conversion unit to the second storage unit;
A first reset unit for resetting the charge accumulated in the first accumulation unit;
A first amplifying unit for amplifying and outputting the charge accumulated in the first accumulating unit;
A first connection for transmitting the output of the first amplifier to a first output signal line;
A second reset unit for resetting the charge accumulated in the second accumulation unit;
A second amplifying unit for amplifying and outputting the charge accumulated in the second accumulating unit;
A second connection for transmitting the output of the second amplification section to a second output signal line;
A plurality of pixels each having a pixel portion in which the pixels are two-dimensionally arranged in a matrix,
When capturing a still image, the photoelectric conversion units of all the pixels included in the pixel unit are collectively exposed, and the first transfer unit of all the pixels included in the pixel unit at the timing of completion of exposure. The photoelectric charge accumulated in the photoelectric conversion unit is transferred only to the first accumulation unit, and the charge accumulated in the first accumulation unit is transferred to the first amplification unit, It reads out as an optical signal via the first connection portion and the first output signal line, and the charge accumulated in the second accumulation portion is converted into the second amplification portion and the second amplification portion. A control unit that controls to read out as an optical noise signal through the connection unit and the second output signal line;
An imaging apparatus comprising: The controller further drives the first reset unit and the second reset unit before collectively exposing the photoelectric conversion unit, and then resets the reset signal of the first storage unit and the second reset unit. Read the reset signal of the storage unit of
Generating still image data that is a difference between the optical signal and the reset signal of the first storage unit, and correction data that is a difference between the optical noise signal and the reset signal of the second storage unit. The imaging apparatus according to claim 1, further comprising: an image processing unit that generates corrected still image data that is a difference between the still image data and the correction data. The pixel belongs to any one of a plurality of fields;
The control unit outputs the optical signal, the optical noise signal, the reset signal of the first storage unit, and the reset signal of the second storage unit to the first of the pixels belonging to the field. The imaging apparatus according to claim 2, wherein control is performed so that reading is performed for each field from one storage unit and the second storage unit. The control unit exposes the photoelectric conversion unit of the pixel before reading out the reset signal of the first storage unit and the reset signal of the second storage unit for each field, and at the timing of completion of exposure. Driving the first transfer unit or the second transfer unit of the pixel to transfer the photoelectric charge accumulated in the photoelectric conversion unit only to the first accumulation unit or the second accumulation unit, After reading out the electric charge accumulated in the first accumulation unit or the second accumulation unit as an optical signal for live view display, and further reading out the optical signal and the optical noise signal for each field The photoelectric conversion unit of the pixel is exposed, and at the timing of exposure completion, the first transfer unit or the second transfer unit of the pixel is driven, and the photoelectric charge accumulated by the photoelectric conversion unit is First storage 4. Or the second storage unit, and the charge stored in the first storage unit or the second storage unit is read as an optical signal for live view display. The imaging device described in 1.

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